1. Field of the Invention
An aspect of the present invention relates to a method for manufacturing an optical unit.
2. Description of the Related Art
Recently, an image quality with a higher definition is desired for a multi-color image forming apparatus. Accordingly, speeding up progresses year by year and use as an on-demand printing system is being provided for simple printing. Specifically, a two-dimensional array element with a configuration of two-dimensionally arrayed surface-emitting lasers is used so that it may be possible to set a sub-scanning interval on a photoconductor body at 1/n of a recording density and it may be possible to form a matrix configuration with a unit pixel of plural or n×m dots (for example, Japanese Patent Application Publication No. 2004-006592 and Japanese Patent Application Publication No. 2007-079295).
Furthermore, in an optical system which generally has a semiconductor laser element, etc., including a surface-emitting laser element, returned light, that is, reflected light from a lens or a cover glass, may return to and be incident on a laser element having emitted light, and in such a case, a variation in an amount of light from the laser element may be caused. Hence, a structure of an inclined cover glass for preventing such a variation in an amount of light is disclosed for example, Japanese Utility Model Application Publication No. 61-059368 and Japanese Utility Model Application Publication No. 62-058066).
Meanwhile, the number of electrodes is also large in a case of a surface-emitting laser element such as a surface-emitting laser array with two-dimensionally arrayed surface-emitting lasers, and if installation into a housing such as a can package used for a general semiconductor laser, etc., is conducted, a shape of such a housing may be large. Hence, for a housing for placing a surface-emitting laser array chip, a structure provided by combining a concave ceramic package made of a ceramic and a cover glass is devised, and furthermore, a structure provided by placing a light-receiving element inside of a concave ceramic package is devised.
When a surface-emitting laser array chip and a light-receiving element are placed in such a housing with a structure provided by combining a concave ceramic package and a cover glass, a surface-emitting laser array chip with a surface-emitting laser array formed thereon, etc., is fixed on a concave bottom of a ceramic package, and subsequently, an electrode provided in the surface-emitting laser array chip and an electrode provided on the concave bottom of the ceramic package are connected by wire bonding to conduct it. Additionally, a cover glass is subsequently placed on a top of a concave ceramic package.
Herein, a relative positional relationship between the surface-emitting laser array chip and a light-receiving element, and a relative positional relationship between the surface-emitting laser array chip and light-receiving element and the cover glass may be important. Meanwhile, when the surface-emitting laser array chip and the light-receiving element are placed in the ceramic package, placement is conducted with reference to an external side wall of the ceramic package, etc. On the other hand, the surface-emitting laser array chip and the light-receiving element are elements which are operated by electricity, etc., and accordingly, connection is conducted by wire bonding, wherein a wiring line formed on the ceramic package is recognized by image recognition in the wire bonding and connection is conducted by a bonding wire based on such a recognized wiring line, etc.
Furthermore, a ceramic package is generally fabricated by dividing a substrate with plural ceramic packages formed thereon. A concave portion and a convex portion are formed on a side face portion of a ceramic package fabricated by being divided accordingly, and hence, when a surface-emitting laser array chip which is a light-emitting element and a light-receiving element, etc., are placed with reference to such a side face portion, such elements, etc., may not be placed at a desired position on the ceramic package. In such a case, in a process of conducting wire bonding, it may be impossible to conduct connection by a desired bonding wire or the surface-emitting laser array chip or the light-receiving element may be broken. Additionally, for a method for forming a side face portion of a ceramic package in a desired shape, a method for cutting a ceramic package by dicing or a method for polishing a side face portion of a post-divided ceramic package may be conceived of, but any of the methods may require a lot of time and cost and hence, may not be practical.